To answer this item, we let x be the number that is not unknown in this item such that the situation in this problem can be expressed as follows,
x - 9.3 = 68.91
Adding 9.3 to both sides of the equation,
x - 9.3 + 9.3 = 68.91 + 9.3
Simplifying,
x = 78.21
The answer to this item is 78.21, this I think is the first choice except that it is mistakenly written as 7.21 only.
